[tex]h = 80 \ cm = 0,8 \ m\\W = 160 \ J\\g = 10\frac{m}{s^{2}}\\m = ?\\\\W = E_{p} = mgh\\\\W = mgh \ \ /:gh\\\\m = \frac{W}{g\cdot h}\\\\m = \frac{160 \ J}{10\frac{m}{s^{2}}\cdot0,8 \ m} = \frac{160 \ kg\cdot\frac{m^{2}}{s^{2}}}{8\frac{m^{2}}{s^{2}}} = 20 \ kg[/tex]
